1. Technical Field
The present invention relates to a projection system, a projector, a method of controlling the projectors, and a program therefor.
2. Related Art
In the related art, a tiling projection that projects a plurality of projected images arranged on a screen using a plurality of projectors (projection image display apparatus) (for example, see patent document JP-A-6-178327; JP-A-9-326981; JP-A-2001-339672; Pamphlet of International Publication No. 99/31877; JP-A-2001-251651).
In the tiling projection, images to be projected by the respective projectors are projected in temporal synchronization in some way. In each projector, image information is written in sequence from an uppermost scan line with a vertical synchronous signal and a horizontal synchronous signal. Therefore, when displaying images so as to be arranged one on top of another, wiring of an area where the upper image and a lower image are overlapped with each other is shifted by approximately one vertical sync. When information of a new frame is being written in the lower image, the image of one frame before is still written in the upper image.
Therefore, in the tiling projection in which the images are projected one on top of another, there is a problem such that a difference of approximately one frame occurs in writing in the overlapped area and hence image information of the different frames are displayed on the same area. In particular, when an image of high speed movement is projected, the image on the overlapped area is disadvantageously defocused. Even though it is short in terms of duration and hence it does not become an issue, a shift by one horizontal cycle occurs in the overlapped area also in the tiling projection in which the images are arranged side by side.
Therefore, as a method of solving the problem occurred in the overlapped area of the upper and lower images, the following method is proposed.
In other words, the write timing of the lower image is delayed so that writing of the lower image starts when writing of the upper image reaches the overlapped area, whereby display of the image information of the different frames in the overlapped area is prevented (For example, see JP-A-2001-222269.
However, with the method disclosed in JP-A-2001-222269, a delay of an amount corresponding to about one frame occurs even with only two images of upper and lower screens. Therefore, for example, in the case in which a big screen display is produced using four projections in the vertical direction and four projections in the lateral direction, that is, sixteen (4×4) projections in total, a display of the amount corresponding to four frame occurs between the uppermost screen and the lowermost screen, and hence a projected image which gives a very strange feeling results as a whole.